1. Field of the Invention
The present invention relates to a method and an apparatus for processing an end of a cable, in particular of a shielded cable.
2. Description of the Related Art
The prior art shielded cable has an insulated wire covered with a conductive sheath, and has the conductive sheath covered with an insulating sheath. The prior art shielded cable is used mainly as an antenna cable for an automotive vehicle or for transmitting and receiving signals in communication equipment.
The conductive sheath in the prior art shielded cable is made of a so-called woven sheath which is a tube of woven fine metal wires. There are single-layer woven sheaths and multi-layer woven sheaths.
The prior art shielded cable with the above-described woven sheath requires a specified processing to an end of the shielded cable. The insulated wire then must be connected with a specific electrical wiring system, and the woven sheath must be connected with another electrical wiring system (mainly ground potential). However, if the end of the shielded cable is processed manually, efficiency is poor and finished shielded cables vary. This results in a poor yield.
In view of the above problem, methods and apparatuses for applying processing to an end of a shielded cable have been proposed. There are roughly two known technical measures.
The first technical measure concerns methods and apparatuses as disclosed in Japanese Unexamined Patent Publications No. 5(HEI)-146022 and 6(HEI)-22427, according to or in which a woven sheath is exposed by making an annular cut in an insulating sheath of a shielded cable, the exposed woven sheath is caused to bulge radially out, and the outer edge of the bulged portion is cut. Known methods for bulging the woven sheath out include a method according to which the woven sheath is pushed manually toward the base end of the peeled insulating sheath, and a method according to which a cut piece of the insulating sheath is slid on the woven sheath to move the woven sheath toward the base end of the peeled insulating sheath.
The second technical measure concerns methods and apparatuses as disclosed in Japanese Unexamined Patent Publication No. 2-273472, according to or in which a part of a woven sheath exposed by peeling is perforated and a core is drawn through the perforation.
In the first conventional methods and apparatuses described above, processing is difficult since the woven sheath is bulged out annularly or radially. In other words, it is often difficult to automate an operation step of radially bulging the woven sheath out, which results in a poor yield. Particularly, if the woven sheath is multi-layered, there is a disadvantage that the woven sheath is buckled and cannot be bulged out to have a desired shape according to the method for moving the woven sheath. Further, the first technical measure is not preferable because it necessitates many operation steps and results in much waste material.
On the other hand, in the second methods and apparatuses, it is difficult to insert a needle between the woven sheath and the insulated wire. In other words, the needle needs to be pushed while prying or forcibly widening the woven sheath in order to be inserted between the woven sheath and the insulated wire. Such a needle inserting operation requires relatively complicated movements of the needle, and efficiency cannot be improved.
Furthermore, in the case of connecting a terminal, for example, with an insulated cable, it is necessary to peel a part of an insulation coating to expose a conductor at an end of the cable. In an apparatus in which this cable end processing is mechanized, a positioned cable is held by clamps, and an annular cut is made in an insulation coating by piercing a pair of opposed peeling blades into the insulation coating. Thereafter, the cut piece of the insulation coating is peeled off by relatively moving the peeling blades and the cable. Most apparatuses adopt this method for the peeling of the insulation coating at the cable end.
The peeling of a single-core insulated cable can be completed only by peeling the insulation coating once. However, a multiple-core insulated cable needs to be peeled such that the respective core wires are first exposed at their ends by peeling an outer sheath, and then conductors are exposed by peeling the insulation coatings of the respective core wires. Thus, peeling needs to be performed several times to process an end of one cable.
FIG. 21(a)shows a prior art shielded cable A in which an insulated wire comprised of a conductor S1 and an insulation coating S2 is coated with a woven sheath S3, and the woven sheath S3 is covered with an outer sheath S4. The prior art shielded cable A needs to have its end processed as follows. First, the outer sheath S4 is peeled to expose the woven sheath S3 at the end. Subsequently, the insulated wire is exposed by, for example, turning the exposed woven sheath S3 up around the outer sheath S4. Then, the insulation coating S2 is peeled to expose the conductor S1 in the middle. Accordingly, peeling is performed twice for processing an end of one cable.
In the case that a great number of cables are processed using the end processing apparatus, handling of the scrap insulation coatings peeled off becomes a problem.
Scattering of the scrap insulation coatings deteriorates a work environment and, in a worse case, may be jammed in the apparatus, causing the apparatus to stop.
In view of the above, a scrap collecting box is installed in the vicinity of peeling blades so that the scrap insulation coating peeled off the cables can drop into the collecting box.
Alternatively, there has been proposed an apparatus in which a suction pipe is arranged on an extension of the cable end and near the peeling blades to collect the scape insulation coatings peeled off the cables by suction (Japanese Unexamined Patent Publication No. 7-95710).
A collection error may occur with the method for collecting the dropped scrap insulation coatings by the collecting box, and the scattering of the scrap cannot be prevented sufficiently.
On the other hand, since cable end is not guided while peeling is performed in the apparatus disclosed in the above publication for collecting the scrap insulation coatings by the suction pipe, there may be a variation in the quality of the processed cable ends. To avoid this problem, such a method may be adopted, according to which the cable end is supported by a guide member before the peeling blades are pierced into the insulation coating. The guide member is replaced by the suction pipe after the insulation coating is cut, and then the cut piece of the insulation coating is peeled off and collected by the suction pipe. However, such a method increases the number of operation steps of the apparatus, thereby reducing an operation efficiency.
Besides, since the suction pipe is wide open in the apparatus of the above publication, the scrap insulation coating may bounce in the suction pipe and jump out of it. Further, the wide opening of the suction pipe causes a large loss in section force and, accordingly, requires a suction means to have a large suction capacity.
The present invention was developed in view of the above problems, and an object thereof is to provide cable end processing method and apparatus which enables an improved handling, preferably enabling an automated operation, particularly an automated operation step of widening a woven sheath, or furthermore preferably allowing to completely collect scrap insulation coatings without degrading processing quality and operation efficiency in order to maintain a stable operation of an apparatus and a clear work environment